There are known bending machines for profiles already sheared to size, such as round pieces for reinforcement purposes or suchlike, individual or in bundles, wherein the drawing assembly is stationary and positioned in proximity with the shearing means, such as for example a shears, and bending means, such as for example a rotary bending disk including at least a bending pin and at least an axial contrasting pin.
The nearness of the drawing assembly to the bending means is due to the fact that, among other reasons, the sheared to size straight bars have longitudinal tensions and torsions which are released with the action of bending, making the bar rotate on its longitudinal axis as it advances. This has a negative effect on the quality, precision and planarity of the bends themselves and on the final products obtained.
It is therefore extremely advantageous to limit to a minimum the segment of bar not gripped between the drawing assembly and the shearing or bending means.
At the same time the nearness of the drawing assembly to the bending means makes the operator responsible for loading the machine more exposed to the danger of accidents and injury; in fact, in order to load the profiles into the drawing assembly, for example by removing them from a bundle, the operator has to be very near the shearing means and the bending means, with the risk of being hit by shavings, fragments or the profile itself during the bending step.
Moreover, since the torsions of the bar are released as it advances and is bent, the bent portion can rise up for quite a large amount from the ideal bending plane, with the risk of hitting the operator.
Documents EP-A-0.258.109, GB-A-1.413.143 and FR-A-2.553.314 all refer to shearing and/or bending machines which work metal bars from a coil; they comprise a drawing element movable with alternate motion, with continuous backwards and forwards movements, to unroll on each occasion a desired segment of said metal bars which are wound in a coil and to feed them to the relative machine.
In the machines described in these documents, there is always a straightening assembly between the feeding coil and the drawing assembly; thanks to the action of the straightening assembly, the problems of longitudinal tensions and torsions, which are found in the bending of pre-sheared bars, are largely eliminated.
The Applicant is not aware of bending machines which work pre-sheared profiles and which have at least part of the drawing assembly movable from a first loading position cooperating with an accumulation site for the profiles to a second drawing position wherein they cooperate with the bending unit and with the shearing assembly in order to perform the bending cycle.
The Applicant has devised and embodied the present invention to overcome this shortcoming of the state of the art and to obtain further advantages.